Tricolor LED display system having audio output

ABSTRACT

A tricolor LED display system ( 10 ) is provided having a plurality of multi-color LEDs ( 22 ) that operate as concurrent display and data communication elements. These dual-use tricolor LEDs are coupled to a special-purpose computer system ( 12 ) and audio signal transmitter ( 16 ) for simultaneously controlling the visible display signal from the LEDs, and for modulating audio information onto the visible light signal emitted by the LEDs. A receiver circuit ( 24 ) receives the modulated visible light signal from the LEDs and demodulates the received signal to recover the audio information, which is then presented to a user of the system through an audio interface.

RELATED APPLICATIONS

This application claims priority from provisional application serialnumber U.S. 60/078,685 filed Mar. 20, 1998 in the United States withinone year from the filing date of this application.

FIELD OF THE INVENTION

The present invention relates to the field of LED display systems anddata communications. More specifically, the invention provides atricolor light emitting diode (“LED”) display system in which the LEDsare used as concurrent display and data communication elements fordisplaying visible information and for transmitting modulated audioinformation to an associated receiver.

SUMMARY OF THE INVENTION

A tricolor LED display system is provided having a plurality ofmulti-color LEDs that operate as concurrent display and datacommunication elements. These dual-use tricolor LEDs are coupled to aspecial-purpose computer system and audio signal transmitter forsimultaneously controlling the visible display signal from the LEDs, andfor modulating audio information onto the visible light signal emittedby the LEDs. A receiver receives the modulated visible light signal fromthe LEDs and demodulates the received signal to recover the audioinformation, which is then presented to a user of the system through anaudio interface.

The LED display system preferably includes a transmitter sub-system anda receiver sub-system. The transmitter subsystem may include aspecial-purpose computer, such as a PC, workstation or embeddedcomputer, and an audio signal transmitter, which are both coupled to thepreferred tricolor dot matrix LED display via a special interfacecircuit. The audio signal transmitter preferably includes avoltage-controlled oscillator for modulating the audio signalinformation onto the LEDs of the display. The preferred tricolor LEDdisplay is capable of generating three distinct colors—red, green andamber. The receiver subsystem may include a lens for focusing thetransmitted light from the LEDs onto a photo-detector (or other opticaldetection means), a demodulator circuit for recovering the audioinformation from the modulated visible light signal emitted by thetricolor display, and an audio system for presenting the demodulatedaudio information to a user of the system.

According to one aspect of the invention, a tricolor LED display systemis provided that includes a transmitter sub-system for simultaneouslytransmitting visible display signals and modulated visible light signalsthrough a tricolor LED display, wherein the modulated visible lightsignals carry modulated audio information; and a receiver sub-system forreceiving the modulated visible light signals and for demodulating thevisible light signals to recover the transmitted audio information.

According to another aspect of the invention, a tricolor LED displaysystem is provided that includes a tricolor LED dot matrix displayhaving a plurality of tricolor LEDs; means for applying a display signalto the tricolor LEDs to generate a visible signal pattern; and means forapplying an audio signal to the tricolor LEDs to emit a modulatedvisible light signal that carries the audio signal.

Still another aspect of the invention provides an interface circuit forcontrolling a tricolor LED display, comprising: a row counter decodesystem coupled to a modulated audio signal for controlling the rowselection of the LEDs in the tricolor LED display; and a segment counterdecode system coupled to display information for controlling the segmentselection of the LEDs in the tricolor LED display. The interface mayalso include: a parallel port interface for receiving the displayinformation, the display information including display data andaddressing information for the LED display; an address comparison unitfor comparing the addressing information for the LED display with systemaddressing information generated by the row counter decode system andthe segment counter decode system; and a pattern storage system forstoring the display data when the address comparison unit indicates thatthe addressing information for the LED display is the same as theaddressing information generated by the row counter decode system andthe segment counter decode system.

It should be noted that these are just some of the many aspects of thepresent invention. Other aspects not specifically listed will becomeapparent upon reading the detailed description set forth below.

The present invention provides many advantages overly presently knowndata communication systems and LED display systems. Not all of theseadvantages are simultaneously required to practice the invention asclaimed, and the following list is merely illustrative of the types ofbenefits that may be provided, alone or in combination. A primaryadvantage of the present invention is in the use of tricolor LEDs as theconcurrent display and data communication elements. This provides a datacommunication system that is more reliable. Because tricolor LEDs areutilized in the display of the invention, the background of the displaycan be energized using a color that is different from the maincharacters (or messages) being displayed. LEDs in a given row(regardless of color state) can be modulated with the same audioinformation. By constructing the system in this manner, there willalways be an LED lit up in each row, thus ensuring more reliable datatransmission over single-color displays, in which certain LEDs in a rowhave to be shut off in order to provide the correct visible display. Inaddition to this reliability advantage, the pattern or graphicsdisplayed by the tricolor display will also be more attractive andflexible as more colors can be used for the display.

Other advantages of this invention include, for example: (1) a brighterdisplay than a single-color LED display; (2) reduced noise on themodulated signal due to the design of the interface circuit and itssynchronization source; (3) permits text scrolling with no effect on thetransmitted modulated signal; and (4) relaxed design constraints on thereceiver system.

These are just a few of the many advantages of the present invention, asdescribed in more detail below in terms of the preferred embodiments. Aswill be appreciated, the invention is capable of other and differentembodiments than those specifically set forth below, and its details arecapable of modifications in various respects, all without departing fromthe spirit of the invention. Accordingly, the drawings and descriptionof the preferred embodiments are to be regarded as illustrative innature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a preferred tricolor LED display systemaccording to the present invention, including a transmitter sub-systemand a receiver sub-system;

FIG. 2 is a block diagram of an audio signal transmitter, which is partof the preferred transmitter sub-system shown in FIG. 1;

FIG. 3 is a block diagram of a preferred receiver sub-system;

FIG. 4 is a block diagram of a preferred interface circuit, which ispart of the referred transmitter sub-system shown in FIG. 1; and

FIG. 5 is a schematic of a tricolor dot matrix display using lightemitting diodes.

DETAILED DESCRIPTION OF THE DRAWINGS

Turning now to the drawing figures, FIG. 1 sets forth a block diagram ofa preferred tricolor LED display system 10 according to the presentinvention, including a transmitter sub-system 12-22 and a receiversub-system 24. The transmitter sub-system includes a computer 12, whichmay be operating an executive computer program 14, an audio signaltransmitter 16, an interface circuit 18, and a tricolor LED display 20comprising a plurality of tricolor LEDs 22. The receiver sub-system 24is described in more detail below in connection with FIG. 3.

The computer 12 could be a PC, workstation, laptop, embedded computer,or any other type of processing system capable of executing a program.The executive computer program 14 runs on the computer 12, and controlsthe visual display of characters, decorative patterns or messages on thedisplay panel 20. The audio signal transmitter 16 (described in moredetail below in connection with FIG. 2) generates the modulated audiosignal that is applied to the LED display 20 in order to cause the LEDs22 to emit the modulated visible light signal that carries the desiredaudio information. The audio signal transmitter 16 and the computer 12are coupled to the tricolor LED dot matrix display 20 by the interfacecircuit 18. The coupling between the computer 12 and the interfacecircuit 18 is preferably a parallel data port for transporting paralleldata from the computer 12 to the interface circuit 18, which uses thisdata to generate the appropriate display message on the tricolor LEDdisplay matrix 20. The preferred interface circuit is described in moredetail below in connection with FIG. 4. The purpose of this circuit isto simultaneously control the display and data communication functionsof the LED display 20.

The receiver sub-system 24 includes elements for receiving the modulatedvisible light signal from the tricolor display 20, and for demodulatingthe received signal in order to recover the desired audio information.The preferred elements of the receiver sub-system are described in FIG.3.

FIG. 2 is a block diagram of an audio signal transmitter 16 that formspart of the preferred tricolor LED display system shown in FIG. 1. Theaudio signal transmitter includes a source of audio information, suchas, for example, a cassette tape 30 or CD player 32, a voltagecontrolled oscillator (“VCO”) circuit 34 and a buffer circuit 36. Theoutput of the audio signal transmitter is a modulation signal 38, which,when applied to the LEDs 22 of the tricolor LED display 20, causes theLEDs to emit the modulated visible light signal that includes the audioinformation.

The cassette tape 30 or CD player 32 generates audio signals that are tobe transmitted by the LED display 22. This audio signal is then fed tothe VCO 34, which operates as a frequency modulator (“FM”) in order tomodulate the audio signal so that a modulated carrier frequency isproportional to the amplitude of the audio signal. The VCO outputs themodulation signal 38, which is applied to the LEDs 22 in order to turnthe LEDs on/off at a particular frequency corresponding to themodulation signal. This frequency is high enough such that theperceivable light from the LEDs 22 appears to be constantly illuminatedto the human eye. Thus, to an observer there is no indication that theLEDs of the tricolor display are operating in a concurrent manner.

FIG. 3 is a block diagram of a preferred receiver sub-system 24. Thereceiver sub-system 24 includes a lens 42, photo-detector 44, FMdemodulator 46 and a speaker 50 and/or headphones 48. The lens 42collects the visible light emitted by the LED display 20, including themodulated visible light signal. These light rays are then focused onto aphoto-detector 44, or other type of optical detection means. Thephoto-detector 44 converts the modulated visible light signal into anelectrical signal. The FM demodulator 46 then demodulates the modulatedsignal into the original audio signal generated by cassette 30 or CDplayer 32. A speaker 50, headphones 48 or ear jack can be used for thedelivery of the audio messages or music sent from the transmitter 16.The receiver sub-system could be battery powered, such that it isportable, or could be powered by any other type of electrical system.

FIG. 4 is a block diagram of a preferred interface circuit 18 that formspart of the preferred transmitter sub-system shown in FIG. 1. Thiscircuit 18 may include a row counter decode system 60; a parallel portinterface circuit 64; a status indicator 66; a segment counter decodesystem 68; a pattern storage system 72; an address comparison circuit78; and an oscillator 80. The circuit may also include one or morebuffer/register circuits 62, 70, 74, 76. Three of these buffer/registers62, 74 and 76 generate the row data, segment data and segment selectionsignals, respectively, that control the tricolor LED display 20. Theinterface circuit 18 is coupled to the computer 12 by parallel portinterface 64 and to the audio signal transmitter by modulation signal38.

The modulation signal 38 from the audio signal transmitter 16 is coupledto the row counter decode system 60, which is in turn coupled to the rowdata input on the tricolor LED display 20 by optional buffer/register62. The row counter decode system 60 is used to switch among the variousrows of the LED display 62, and includes a counter driven by themodulation signal 38, and a decoder for appropriate row selection.

The segment counter decode system 68 is driven by oscillator 80. It isused to switch among the segments of the LED display 20. The segmentcounter decode system 68 is coupled to the segment selection input onthe tricolor LED display 20 by optional buffer/register 76. This circuit68 includes a counter, which is driven by a fast oscillator 80, and adecoder for segment selection.

The pattern storage system 72 is used to store the LED display patternof every row and segment in the matrix 20. It is preferably an SRAM,although other types of solid state memory could also be used for thispart. The data pattern stored in the pattern storage system 72 isprovided by the computer system 12 via parallel port interface 64.

The address comparison unit 78 takes as inputs the current row address(from the row counter decode system 60) and the segment address (fromthe segment counter decode system 68) and compares these addresses tothe address signal from the parallel port interface 64. It compares thesystem-generated address (based on the two counter systems 60, 68)against the address sent out by the computer 12. This is done to ensurethat the SRAM data stored in the pattern storage system 72 and thedisplay 20 will not be disrupted until the LEDs are in the inactivestate (off state). Until these address values match, new data is notwritten into the pattern storage system 72. The address comparison unit78 includes a bit comparator (for comparing the bits of the addressvalues) and a data register 70. The register holds the message data fromthe parallel port interface 64 until the system is ready to write datato the SRAM (i.e., when the address values match). When this occurs, theaddress comparison unit asserts the “/WE” line to the SRAM 72, whichcauses the register data 70 to be written into the pattern storagesystem 72. The pattern storage system outputs the segment data to theappropriate LEDs in the tricolor display 20 through an optionalbuffer/register circuit 74.

The status indicator 66 includes a D-type flip-flop with asynchronouspreset and clear inputs. The non-inverted flip-flop output pin (strobepin) is used to indicate a successful write operation. When this occurs(based on a signal from the address comparison unit 78), the strobe pinwill be set high, which is then transmitted to the computer 12 via theparallel port interface 64 so that the computer 12 can send out the nextdata.

Operationally, the interface circuit 18 updates the display pattern ofthe tricolor LED display 20 as follows. First, the data from thecomputer 12 is latched into a register 70. However, the data will not besent to the SRAM 72 input pins or the segment register 74 input pins soas not to disrupt the normal LED display process. Second, the addressfrom the computer 12 is presented to the address comparator 78, whichcompares this address against the system-generated address from the rowcounter decode system 60 and the segment counter decode system 68. Whenthe addresses match, the output of the comparator is pulled low (/WE),which causes the data stored in the register 70 to be written to thepattern storage SRAM 72. Once the write is complete, a signal (“P═Q”)from the address comparison unit 78 is sent to the status indicatorcircuit 66, which sets the strobe output high, thus informing thecomputer 12 that the write succeeded, and that additional data may bepresented to the interface circuit 18.

Having described the preferred circuit structure of the interfacecircuit 18, it is instructive to consider two additional operationalcharacteristics of this design that provide advantages over presentlyknown LED display systems. The first advantage is the use of multipleclock signals for the LED display, including a high-speed oscillatorclock 80 and a modulation clock signal 38. Whenever the modulationsignal changes, the active row of the LED display 20 will also bechanged. Thus, the row represents a bit of information. The preferredfrequency of the modulation signal is 100 kHz. Audio signal informationis modulated onto this signal by the VCO 34 of the transmittersub-system, thus resulting in a frequency range of 100=44.1 kHz.

The other timing signal used in the preferred interface circuit 18 isgenerated from the high-speed oscillator 18. In the preferredimplementation, a 12 MHz oscillator frequency is used, although otherfrequencies could also be selected. This signal is used to switchbetween different segments of the tricolor LED display 20 (i.e.,different colors in different characters). The segment clock shouldoperate at a higher frequency than the modulation signal clock 38 sothat before the modulation signal 38 is changed (i.e., before the activerow is switched), all the segments have been scanned at least once andupdated. Otherwise, some segments will not be lit as expected.

While the common signals 92 (“row”) are changed at the frequency of themodulation signal (e.g., 100 kHz ), the segment signals 90, 94(“column”) are changed at the higher frequency of about 12 MHz. However,this 12 MHz may be divided by the segment counter 68 so that it isoperating at 6 MHz. In addition, only half of the 100 kHz period of themodulation signal is used for segment selection. Therefore, during theperiod that a row is active, the number of times that the segmentaddress is changed is approximated by: $\begin{matrix}{{\frac{6M}{100k}*\frac{1}{2}} = 30} & \lbrack 1\rbrack\end{matrix}$

The second operational characteristic of the preferred interface circuit18 is that updating of the pattern data is carried out during the periodthat the LEDs are in the off state. This eliminates any noise on theemitted LED signals by synchronizing the circuit with the modulationsignal 38, including the time when the pattern is updated. The interfacecircuit 18 updates the display only when the row input to the LED 20 isinactive. In this manner, no noise will be injected into the modulationsignal because no data will be transmitted during the pattern updateprocess.

FIG. 5 is a schematic of a tricolor dot matrix 20 display using lightemitting diodes 22 that are capable of emitting three different colors.These colors are preferably red, green and amber. The individual LEDs 22are coupled to common signals 92, which tie the LEDs in a given rowtogether, and two segment signals, one for red 90 and another for green94. To energize an LED, the common signal 92 for that row is held low.Then, if a red signal is to be emitted, just the red segment 90 for theparticular column is held high. If a green signal is to be emitted, justthe green segment 94 for the particular column is held high. And if anamber signal is to be emitted, both the red 90 and green 94 segments areheld high.

The software program 14 used for the display control and pattern updateof this tricolor LED dot matrix display 20 operates as follows. For thewrite cycle, data is first put onto the parallel port bus coupling thecomputer 12 to the interface circuit 18, which latches this data. Thecorresponding address (i.e., row and segment data) is then put onto thesame bus by the program 14. This address is compared against thesystem-generated address by the interface circuit 18. If the addressesmatch, then the message data will be written to the pattern storagesystem 72 of the interface circuit 18 at that address. A signal will besent back to the computer 12, indicating a successful write. Since allthe LEDs are then illuminated, it is now possible to introduce displayeffects, such as scrolling into the system.

The benefits of this invention can be applied to a large variety ofapplications. In an indoor environment, a user with an appropriatereceiver system 24 could listen to the audio messages broadcast throughthe tricolor LEDs 22 of the dot matrix display 20. A quiet atmospherecan be maintained. A major advantage over a conventional broadcastingsystem is that an individual with a receiver has the freedom of choicein receiving specific messages without hearing any unwantedannouncement, music or commercials.

In an outdoor environment, for example in front of a business orcommercial institution on the street, the light emitted from thetricolor dot matrix LED display 20 could be used to optically transmitaudio information to a user with a receiver and headphones located somedistance away from the institution. With this invention, all commercialbillboards could be used to transmit additional information such asdaily specials, discounts, latest attractions or any merchandise,reservation telephone numbers, etc.

The preferred embodiments and several applications of the inventivesystem described above are presented only by way of example and are notmeant to limit the scope of the present invention, which is defined bythe claims. Other elements and steps could be used in place of thoseshown.

What is claimed:
 1. A tricolor LED display system, comprising: a transmitter sub-system for simultaneously transmitting visible display signals and modulated visible light signals through a tricolor LED display, wherein the modulated visible light signals carry modulated audio information; and a receiver sub-system for receiving the modulated visible light signals and for demodulating the visible light signals to recover the transmitted audio information.
 2. The system of claim 1, wherein the tricolor LED display is capable of displaying red, green and amber colors.
 3. The system of claim 1, wherein the receiver sub-system includes: an optical sensor for receiving the modulated visible light signal from the tricolor LED display; a demodulator coupled to the optical sensor for demodulating the modulated visible light signal to recover the transmitted audio signal; and a speaker coup led to the audio signal.
 4. The system of claim 3, wherein the receiver sub-system further includes a lens for focusing light emitted by the tricolor LED display onto the optical sensor.
 5. The system of claim 3, wherein the optical sensor is a photo-detector.
 6. A tricolor LED display system, comprising: a transmitter sub-system for simultaneously transmitting visible display signals and modulated visible light signals through a tricolor LED display, wherein the modulated visible light signals carry modulated audio information; and a receiver sub-system for receiving the modulated visible light signals and for demodulating the visible light signals to recover the transmitted audio information; the transmitter sub-system including: a computer system for generating display information; an audio signal transmitter for generating a modulated audio signal; and an interface circuit coupled to the computer system and the audio signal transmitter for applying the display information and the modulated audio signal to the tricolor LED display.
 7. The system of claim 6, wherein the computer system is coupled to the interface circuit through a parallel port interface.
 8. The system of claim 6, further including an executive computer program operating on the computer system for controlling the generation of display information.
 9. The system of claim 6, wherein the audio signal transmitter includes: a source of audio information for generating an audio signal; and a modulator coupled to the source of audio information for generating the modulated audio signal.
 10. The system of claim 9, wherein the modulator is a voltage controlled oscillator.
 11. The system of claim 10, wherein the voltage-controlled oscillator operates as a frequency modulator.
 12. The system of claim 6, wherein the interface circuit includes: a row counter decode system coupled to the modulated audio signal for controlling the row selection of the LEDs in the tricolor LED display; and a segment counter decode system coupled to the display information for controlling the segment selection of the LEDs in the tricolor LED display.
 13. The system of claim 12, herein the interface circuit further includes: a parallel port interface for receiving the display information, the display information including display data and addressing information for the LED display; an address comparison unit for comparing the addressing information for the LED display with system addressing information generated by the row counter decode system and the segment counter decode system; and a pattern storage system for storing the display data when the address comparison unit indicates that the addressing information for the LED display is the same as the addressing information generated by the row counter decode system and the segment counter decode system.
 14. The system of claim 13, wherein the interface circuit further includes: a status indicator coupled to the parallel port interface for generating a write complete signal to the computer system when the display data is written to the pattern storage system.
 15. A tricolor LED display system, comprising: a tricolor LED dot matrix display having a plurality of tricolor LEDs; means for applying a display signal to the tricolor LEDs to generate a visible signal pattern; and means for applying an audio signal to the tricolor LEDs to emit a modulated visible light signal that carries the audio signal.
 16. An interface circuit for controlling a tricolor LED display, comprising: a row counter decode system coupled to a frequency-modulated audio signal for controlling the row selection of the LEDs in the tricolor LED display; and a segment counter decode system coupled to display information for controlling the segment selection of the LEDs in the tricolor LED display.
 17. An interface circuit for controlling a tricolor LED display, comprising: a row counter decode system coupled to a modulated audio signal for controlling the row selection of the LEDs in the tricolor LED display; a segment counter decode system coupled to display information for controlling the segment selection of the LEDs in the tricolor LED display; a parallel port interface for receiving the display information, the display information including display data and addressing information for the LED display; an address comparison unit for comparing the addressing information for the LED display with system addressing information generated by the row counter decode system and the segment counter decode system; and a pattern storage system for storing the display data when the address comparison unit indicates that the addressing information for the LED display is the same as the addressing information generated by the row counter decode system and the segment counter decode system. 